A functional fluid is a term which encompasses a variety of fluids including but not limited to tractor fluids, automatic transmission fluids, manual transmission fluids, hydraulic fluids, power steering fluids, fluids related to power train components and fluids which have the ability to act in various different capacities. It should be noted that within each of these fluids such as, for example, automatic transmission fluids, there are a variety of different types of fluids due to the various transmissions having different designs which have led to the need for fluids of markedly different functional characteristics. One type of functional fluid is generally known as a tractor fluid which can be used in connection with various types of tractor equipment in order to provide for the operation of the transmission, gears, bearings, hydraulics, power steering, mechanical power take-off and oil immersed brakes of the tractor.
The components included within a functional fluid such as a tractor fluid must be carefully chosen so that the final resulting fluid composition will provide all the necessary characteristics required and pass a variety of different types of tests. In general, a tractor fluid must act as a lubricant, a power transfer means and a heat transfer means.
Tractor fluids have a number of important specific characteristics which provide for their ability to operate within tractor equipment. Such characteristics include the ability to provide proper frictional properties for preventing wet brake chatter of oil-immersed brakes while simultaneously providing the ability to actuate wet brakes and provide power take-off (PTO) clutch performance. A tractor fluid must provide sufficient antiwear and extreme pressure properties as well as water tolerance/filterability capabilities.
As manufacturers set new standards for functional fluids, especially in demanding high performance for wear and extreme pressure properties while at the same time using thinner oil for improved low temperature performance, new challenges are put in fluid formulations.
The extreme pressure (EP) properties of tractor fluids are demonstrated by the ability of the fluid to pass a spiral bevel test as well as a straight spur gear test. The tractor fluid must pass wet brake chatter tests as well as provide adequate wet brake capacity when used in oil-immersed disk brakes which are comprised of a bronze, graphitic composition and asbestos. The tractor fluid must demonstrate its ability to provide friction retention for power shift transmission clutches such as those clutches which include graphitic and bronze clutches.
U.S. Pat. No. 5,062,975 discloses a tractor fluid comprising a base oil with an additive package mixed therein. The additive package comprises (1) a calcium overbased sulfonate; (2) an EP/antiwear agent being a zinc salt of dialkyl phosphorodithioic acid; (3) a borated epoxide; and (4) a carboxylic solubilizer.
U.S. Pat. No. 5,284,591 discloses components (1) through (4) as recited in the paragraph immediately above in addition to (5), a sulfurized olefin.
U.S. Pat. No. 4,792,410 discloses a manual transmission fluid comprising
(a) a borated overbased alkali or alkaline earth metal salt selected from the group consisting of sulfonates, phenates, oxylates, carboxylates and mixtures thereof; PA1 (b) a friction modifier selected from the group consisting of fatty phosphites, fatty acid amides, borated fatty epoxides, fatty amines, glycerol esters and their borated derivatives, borated alkoxylated fatty amines, sulfurized olefins and mixtures thereof; and PA1 (c) an oil of lubricating viscosity, wherein such lubricants have excellent static and dynamic frictional characteristics. The lubricant fluids are particularly useful in reducing double detent and clashing during manual transmission shifting. PA1 (1) a majority of a lubricating oil, wherein the functional fluid from said oil has at least 4 cSt kinematic viscosity at 100.degree. C. and a -40.degree. C. Brookfield viscosity of less than 20,000 cP. Also included in the fluid is an additive package which enhances gear antiwear performance of the fluid. The oil can comprise up to about 97 weight percent of said fluid. PA1 (2) an alkali or alkaline earth metal salt complex, said complex selected from the group consisting of: PA1 (3) an EP/antiwear agent comprising zinc salts of dialkylphosphorodithioic acid and 2-ethylhexanoic acid treated with triphenylphosphite or an olefin to reduce sulfur; and PA1 (4) a borated epoxide. PA1 (a) mixing an overbased sulfonate and any required inert liquid medium, PA1 (b) borating the mixture (a) with a borating agent at a temperature less than that at which substantial foaming occurs, PA1 (c) raising the temperature of the mixture (b) to that temperature in excess of the boiling point of water within the mixture (b), PA1 (d) separating substantially all of the water from the reaction mixture and, PA1 (e) recovering the product (d) as a high carbonate content borated product. PA1 (a) mixing an overbased component and any required inert liquid medium, PA1 (b) reacting component (a) in the presence of a borating agent to a boron content of at least about 3% by weight of the product, PA1 (c) reducing the water content of the product (b) to less than about 3% by weight and, PA1 (d) recovering the high carbonate content overbased borated product. PA1 Triphenylphosphite is heated with a zinc dialkylphosphorodithioate or a mixed zinc salt of a dialkylphosphorodithioic acid and a carboxylic acid. The dialkylphosphorodithioic acid used in the preparation of the zinc salt is itself prepared by the reaction of at least one alcohol with phosphorus pentasulfide which contains a stoichiometric excess of sulfur.
U.S. Pat. No. 4,410,438 discloses a lubricant and liquid fuel composition which includes borated epoxides which are indicated as being useful in fluids such as heat exchange fluids, transmission fluids, and hydraulic fluids.
U.S. Pat. No. 3,933,659 discloses a functional fluid for lubricating oil compositions which is comprised of a major amount of an oil of lubricating viscosity and an effective amount of an additive. The additive includes effective amounts of an alkaline succinimide, a group II metal salt of a dihydrocarbyldithiophosphoric acid, a basic sulfurized alkaline earth metal alkyl phenate and a component which is a fatty acid ester, fatty acid amide or fatty acid amine or mixtures thereof. The patent indicates that the lubricating compositions are useful as functional fluids in systems requiring fluid coupling, hydraulic fluid and/or lubrication of relatively moving parts. The lubricating compositions are indicated as being useful as the functional fluid in automatic transmissions and particularly in the automatic transmissions of passenger automobiles.
U.S. Pat. No. 3,953,347 discloses sulfurized compositions prepared by reacting, at about 100.degree.-250.degree. C., sulfur with a mixture comprising (A) 100 parts by weight of at least one fatty acid ester, (B) about 0-50 parts by weight of at least one fatty acid, and (C) about 25-400 parts by weight of at least one aliphatic olefin containing about 8-36 carbon atoms.
U.S. Pat. No. 4, 116,877 discloses an elastomer compatible seal swell additive. The additive may be used in connection with automatic transmission, power transmission fluids and hydraulic steering fluids. The fluid is a mineral lubricating base oil which includes an oil-soluble bis(hydrocarbyl) phosphite ester and an oil-soluble hydrocarbyl substituted phenol wherein a specific weight ratio is maintained with respect to the phosphite and phenol. The patent indicates that the inclusion of these particular additive compounds in the particularly disclosed ratio provides enhanced elastomer compatibility to the fluid.
U.S. Pat. No. 3,929,650 to King et al, issued Dec. 30, 1975, discloses borated overbased alkali metal carbonates of alkali or alkaline earth metal sulfonates. U.S. Pat. No. 3,480,548 to Hellmuth et al, issued Nov. 25, 1969, discloses overbased boronated products.
Published European Patent Application 113,199 published Jul. 11, 1984, discloses a tractor hydraulic fluid which includes oleyl phosphite in a tractor antifriction hydraulic fluid as well as thioethyloctadecenylsuccinate containing tractor hydraulic fluids.
British Patent 1,452,513 dated Oct. 13, 1976, discloses lubricant compositions which include a fatty acid and a fatty acid amide in a wet braking system for tractors which was found to be useful in reducing the amount of noise over a wide temperature range.
British Patent 1,440,261 discloses a composition for reducing the noise in the wet braking systems of tractors. The fluid was comprised of a lubricant oil, and a detergent or dispersant mixed with stearic acid. The composition indicated that it also included alkylene polyamine dispersants, calcium and barium sulfonates and phenates, antiwear-antioxidants and oleic acid.